Fair Value Measurements - Assets and Liabilities Not Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Aug. 31, 2020	Dec. 31, 2019
Senior Notes | 5.75% Senior Notes due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	5.75%
Senior Notes | 5.25% Senior Notes due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	5.25%		5.25%
9% Convertible Junior Subordinated Debentures due 2063
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Stated interest rate (in hundredths)	9.00%	9.00%		9.00%
Carrying Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	$ 3,100	$ 3,100
FHLB Advance	155,000	155,000
9% Debentures	110,204	208,814
Total financial liabilities	1,146,712	1,243,193
Carrying Value | Senior Notes | 5.75% Senior Notes due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	241,255	240,597
Carrying Value | Senior Notes | 5.25% Senior Notes due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	640,253	638,782
Fair Value | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other invested assets	3,100	3,100
FHLB Advance	157,585	160,865
9% Debentures	151,000	273,569
Total financial liabilities	1,251,673	1,392,635
Fair Value | Significant Other Observable Inputs (Level 2) | Senior Notes | 5.75% Senior Notes due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	256,213	261,752
Fair Value | Significant Other Observable Inputs (Level 2) | Senior Notes | 5.25% Senior Notes due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Senior Notes	$ 686,875	$ 696,449